Transition metal imido complexes, especially imido complexes of vanadium, are known from the literature (A. Slawisch, Z. Anorg. Allg. Chem. 374(3) (1970) 291-296; A. Slawisch et al. Z. Naturforsch. B 25(3) (1970), 321; E. A. Maata Inorg. Chem. 23(17) (1984), 2560-2561; F. Preuss et al. Z. Naturforsch., B: Anorg. Chem., Org. Chem. 41B(2) (1986), 185-190; D. Devore et al. J. Am. Chem. Soc. 109 (1987), 7408-7416; F. Preuss et al. Z. Anorg. Allg. Chem. 609 (1992), 45-50; A. Hills et al. J. Chem. Soc., Dalton Trans. 1993, 3609-3617; J.-K. F. Buijink J. Organomet. Chem. 497(1-2) (1995), 161-170; M. P. Coles et al. J. Organomet. Chem. 591(1-2) (1999), 78-87; K. R. Birdswell et al. J. Organomet. Chem. 584(1) (1999), 200-205; F. Preuss et al. Z. Anorg. Allg. Chem. 625 (1999), 901-909; F. Preuss et al. Z. Naturforsch., B: Chem. Sci. 55(1) (2000), 1-4; F. Preuss et al. Z. Naturforsch., B: Chem. Sci. 56(3) (2001), 255-262).
EP-A2-0 518 415 describes vanadium-imidoaryl complexes R—N═VX3, wherein X is a single-bonded ligand, and their use in the preparation of EPDM, an improved incorporation of diene being achieved in comparison with catalysts based on VOCl3. However, those catalysts exhibit markedly lower activities in comparison with VOCl3.
EP-A1-0 532 098 describes vanadium-imidoaryl complexes which are substituted in the ortho-positions of the aryl group, and their use as catalysts for the polymerization of olefins at low AI/V ratios. At high AI/V ratios, identical products having slightly diminished catalytic activities are obtained in comparison with catalysts based on VOCl3.
WO-94/14854-A1 describes vanadium-imidoarylamides as catalysts having high activity for the preparation of EPDM, a dialkyl-substituted aryl group again preferably being used in the imide.
In contrast to sigma-bonded ligands, such as are present in the above-described compounds in addition to the imido group, phosphor-aneiminato groups can act as multi-electron donors and hence, transfer a greater electron density to the central atom (A. W. Johnson et al. “Ylides and Imines of Phosphorous”, J. Wiley & Sons (1993), K. Dehnicke et al. Coord. Chem. Rev. 182 (1999), 19-65).
Vanadyl-phosphoraneiminato complexes were described for the first time by R. Choukroun et al. (Trans. Met. Chem. 4 (1979), 249). They synthesized VOCl2(NPPh3), VOCl(NPPh3)2 and VCl3(NPPh3)2. Roesky, et al. (H. W. Roesky et al.; Z. Naturforsch. 44b (1989), 35; H. W. Roesky, et al. Inorg. Chem. 32 (1993), 5102-5104) describe the synthesis of VOCl2(NPPh2NSMe2O) and VOF2(NPPh3).
WO 00/05237 describes the use of transition metal complexes having phosphoraneiminato ligands as catalysts for the polymerization of olefins. Activation with single aluminum alkyls is described as “comparatively weak”, and activation by aluminoxane or “ionic activators”, such as, for example, trityltetrakis(pentafluorophenyl)borate, is described as markedly better.